The present invention relates to a liquid supply plunger pump and, more particularly, to a constant flow rate liquid supply plunger pump of a compact size for use in an ink liquid supply system of an ink jet system printer of the charge amplitude controlling type.
A constant flow rate ink liquid supply pump is highly required in an ink jet system primter of the charge amplitude controlling type to ensure an accurate printing. When a plunger pump is used in the ink liquid supply system, the ink liquid leakage through a gap formed between the cylinder and the piston must be carefully considered. More specifically, the gap must be accurately controlled to ensure the constant flow rate liquid supply.
Accordingly, an object of the present invention is to provide a compact size plunger pump which ensures the constant flow rate liquid supply.
Another object of the present invention is to provide a constant flow rate plunger pump suited for mass production.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a bush is secured to a cylinder block. A piston is slidably disposed through the bush to define pressure chambers. In a preferred form, the bush is exchangeably secured to the cylinder block through the use of screwed portions formed on an outer surface of the bush and an inner surface of the cylinder block. The outer periphery of the piston is formed to show a high resistance to wear through the use of the surface thermal treatment or an organic film coating such as a tetrafluoroethylene coating.